Acyltransferase and cDNA encoding acyltransferase

ABSTRACT

Essentially pure acyltransferase is provided which is functional to catalyze reaction to form sugar esters. Also provided is isolated gene encoding acyltransferase. Additionally provided is method for forming palmityl esters of glucose comprising reacting 1-O-palmitoyl-β-D-glucose with itself, with glucose or with palmityl partial ester of glucose in the presence of a catalytically effective amount of acyltransferase.

This invention is made in part with Government support under U.S. Department of Agriculture Grants 90-37153-5438 and 91-37300-6566. The Government has certain rights in the invention.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of Ser. No. 60/008,948, filed Dec. 20, 1995.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of Ser. No. 60/008,948, filed Dec. 20, 1995.

TECHNICAL FIELD

This invention is directed to isolation of acyltransferase for use in preparing sugar polyesters and to gene encoding acyltransferase for use in preparing sugar polyesters.

BACKGROUND OF THE INVENTION

Sugar polyesters are a diverse class of molecules including, but not limited to, glucose and sucrose esters of fatty acids and other carboxylic acids.

Partial acylation of the available hydroxyls in the sugar moiety provides feeding deterrent (pest repellent) properties (for use in agriculture), emulsification properties (for use in the food and cosmetic industries) and emollient properties (for use in the cosmetic industry). Six to eight fatty acids esterified to the eight available sucrose hydroxyls provides noncaloric fat substitute.

At present, the sugar polyesters are made through techniques of synthetic organic chemistry.

SUMMARY OF THE INVENTION

The present invention is based on isolation of an acyltransferase from a plant which catalyzes esterification reactions providing sugar esters and sugar polyesters.

In a first embodiment, the instant invention is directed to an essentially pure acyltransferase which comprises the sequence set forth in the Sequence Listing as SEQ ID NO: 8 and to an essentially pure acyltransferase which comprises the sequence set forth in the Sequence Listing as SEQ ID NO: 8 and also the sequences set forth in the Sequence Listing as SEQ ID NOS: 5 and 6.

Based on isolation of the acyltransferase, genes have been isolated which code for acyltransferase. These isolated genes are useful for preparing transgenic yeast or transgenic E. coli for use in manufacturing acyltransferase or for use in preparing transgenic plants transformed to contain gene coding for acyltransferase which produce sugar polyesters and which may be harvested to recover sugar polyesters.

In a second embodiment, the instant invention is directed to an isolated gene encoding an acyltransferase which comprises the sequence set forth in the Sequence Listing as SEQ ID NO: 9.

In a third embodiment, the instant invention is directed to a method of preparing palmitoyl esters of glucose which comprises reacting 1-O-palmitoyl-β-D-glucose with glucose or with palmitoyl partial ester of glucose in the presence of acyltransferase which comprises the sequence set forth in the Sequence Listing as SEQ ID NO: 8 or which comprises the sequence set forth in the Sequence Listing as SEQ ID NO. 8 and also the sequences set forth the Sequence Listing as SEQ ID NOS: 5 and 6.

The term "essentially pure" is used herein to mean meeting the criterion of purified to be free of contaminating protein, i.e., a single protein band or a plurality of protein bands representing different levels of glycosylation of the same protein or a plurality of protein bands representing a protein and subunit or subunits thereof, on a sodium dodecyl sulfate polyacrylamide gel submitted to electrophoresis under reducing, or fully denaturing, conditions and stained with Ponceau stain and/or meeting the criterion of having a specific activity of at least 35 nanokatals mg⁻¹.

DETAILED DESCRIPTION

Acyltransferase herein is coded for by gene of the genome of and is isolated and derived from the wild tomato species Lycopersicon pennelli (LA716), which is available from the Tomato Genetics Resource Center.

To purify this enzyme, leaf extract is prepared from leaves of L. pennelli (LA716) as described in Example I herein and the enzyme is obtained from the leaf extract and is purified therefrom in a succession of five purification steps. The first step in the purification is an ammonium sulfate precipitation step in which protein is precipitated by addition of solid ammonium sulfate, i.e., (NH₄)₂ SO₄. Ammonium sulfate is added to the extract to 80% of saturation. This is followed by centrifugation. The supernatant is retained and dialyzed. The second step in the purification is a polyethylene glycol precipitation step. Polyethylene glycol is added to provide 0.15 g/ml. This is followed by centrifugation. After discarding of the pellet, polyethylene glycol is added again to a final concentration of 0.22 g/ml at which point protein precipitates and is collected by centrifugation. The third step in the purification involves ion exchange on DEAE (diethylaminoethoxy ion exchange moiety) sepharose. A suspension of protein from the second purification step is passed through a column containing DEAE sepharose and then elution is carried out using 0-250 millimolar KCl gradient. The active fractions are pooled and concentrated by ultrafiltration. The fourth step in the purification involves performing affinity chromatography on the concentrated active fractions from the third purification step in a column containing Concanavalin A (a protein which binds sugars, sometimes referred to as ConA). Proteins which are glycosylated bind, and since the acyltransferase being isolated is glycosylated, it binds. This fourth purification step involves washing with Tris-KOH (pH 7.5) plus 10% glycerol as loading buffer and then eluting first with the Tris buffer and 10% glycerol plus 50 mM α-methylglycoside to displace previously bound irrelevant protein and then eluting with the Tris buffer and 10% glycerol plus 100 mM α-methylglycoside to elute the enzyme of interest. The active fractions are pooled and concentrated by ultrafiltration. The fifth step in the purification involves performing HPLC on the concentrated active fractions from the fourth purification step on a chromatofocusing column under a pH gradient of 4-6. Again the active fractions are pooled and concentrated by ultrafiltration.

Assays for enzyme activity are readily carried out by measuring the disproportionation of 1-O-P- ¹⁴ C-isobutyryl!glucose to form 1-O-β- ¹⁴ C-isobutyryl!-di-O- ¹⁴ C-isobutyryl!-glucose, 1-O-β- ¹⁴ C-isobutyryl!-tri-O- ¹⁴ C-isobutyryl!-glucose, i.e., the transfer of the ¹⁴ C!isobutyryl group from 1-O-β- ¹⁴ C-isobutyryl!glucose to other 1-O-β- ¹⁴ C-isobutyryl!glucose, in the presence of sample for which enzyme activity is being determined. A preferred assay involving measuring acyl transfer is described in Example I hereinafter.

Assays for enzyme activity can also be carried out by measuring the anomeric transfer of isobutyryl from 1-O-isobutyryl-β-D-glucose to U-¹⁴ C!-glucose. A preferred assay involving measuring anomeric transfer is as follows. The assay is performed in a total volume of 15 μL which contains 50 mM Hepes pH 7.5, 10 mM dithiothreitol, 2 mM 1-O-isobutyryl-β-D-glucose, 40 μM U-¹⁴ C!-glucose (2×10⁵ cpm) and 1 to 100 ng acyltransferase. The reaction is allowed to proceed at 37° C. for 30 minutes, and then loaded onto a silica gel thin-layer chromatography plate and eluted in chloroform/methanol/water (75:22:3). The thin layer plate is then dried, exposed to autoradiographic film, and upon development of the autoradiographic image, the silica gel at regions corresponding to the migration of di-, tri-, and tetra- ¹⁴ C-isobutyryl!-glucose is scraped from the plate, eluted with methanol and radioactively quantified by liquid scintillation.

The purification of the enzyme is described in detail in Example I hereinafter.

An acyltransferase enzyme purified by the above method was found to consist of two subunits of molecular mass 33 kDa and 22 kDa by sodium dodecylsulfate polyacrylamide gel electrophoresis after the enzyme was prepared under reducing conditions on comparison to migration of proteins of known molecular weight, and to have a native molecular weight of 100,000 Da on a gel permeation column, and an isoelectric point as determined by isoelectric focusing on a 5% polyacrylamide native gel with a 3.5 to 9 pH gradient, of 5.2.

Seven peptide fractions obtained from the acyltransferase by treatment with trypsin and separation of the resulting peptides by reversed-phase high pressure liquid chromatography (HPLC) were determined to have the sequences set forth in the Sequence Listing as SEQ ID NOS: 1-7. A sequence of portion of the acyltransferase consistent with the sequence of isolated gene obtained based on the seven peptide fractions is set forth in the Sequence Listing as SEQ ID NO: 8.

The acyltransferase is functional to catalyze anomeric transfer of the acyl substituent from 1-O-acyl-β-D-glucose to glucose, 2-deoxyglucose, 3-O-methyl glucose or partially acylated glucose and to catalyze disproportionation between two molecules of 1-O-acyl-β-D-glucose resulting in formation of diacylglucose and glucose. The acyl substituent including that in the partially acylated glucose can contain, for example, from 1 to 18 carbon atoms and can be branched or straight chain and saturated or unsaturated and can be, for example, isobutanoyl or lauroyl or palmitoyl.

Reaction with 1-O-palmitoyl-β-D-glucose is considered unexpected since this reaction has not been found in nature.

The reaction involving anomeric transfer of acyl from 1-O-acyl-β-D-glucose to glucose, 2-deoxyglucose, 3-O-methyl glucose or partially acylated glucose is readily carried out using a stoichiometric amount of 1-O-acyl-β-D-glucose in buffer or aqueous media at pH ranging from 6.5 to 7.5 at 20° to 40° C. for 10 to 60 minutes in the presence of a catalytically effective amount, e.g., 0.01 to 1 μg of purified acyltransferase per mmol 1-O-acyl-β-D-glucose.

The reaction involving disproportionation is readily carried out in buffer or aqueous media at pH ranging from 6.5 to 7.5 at 20° to 40° C. for 10 to 60 minutes in the presence of a catalytically effective amount, e.g., 0.01 to 1 μg of purified acyltransferase per mmol 1-O-acyl-β-D-glucose.

The 1-O-acyl-β-D-glucose starting material can be prepared, for example, by condensing α-acetobromoglucose and isobutyric acid followed by deacetylation with sunflower esterase. Alternatively, the 1-O-acyl-β-D-glucose can be prepared by reacting acyl chloride with tetrabenzylglucose in dry benzene at 62° C. and deprotecting according to the procedure of Pfeffer, P. E., et al., J. Org. Chem 41, 2925-2927 (1976).

We turn now to the isolation of gene coding for an acyltransferase which catalyzes esterification reactions providing sugar esters and sugar polyesters. Detached trichomes are prepared from L. pennelli leaves by the dry ice abrasion method as described in Yerger, E. H., et al., Plant Physiol 99, 1-7 (1992). The trichomes are suspended in buffer, total RNA extracted and mRNA purified according to the method described in Hunt, M. D., et al, Plant Molec. Biol. 21, 59-68 (1993). The acyltransferase gene is cloned following procedures described by Frohman, M. A., et al., Proc. Natl. Acad. Sci. USA 85:8998-9002 (1988), and Loh, E. Y., et al., Science 243:217-220 (1980). Gene fragment consisting of an internal portion of the gene coding for the acyltransferase is obtained as follows from the total purified mRNA. Total purified mRNA is reversed transcribed into cDNA using oligo (dT)₁₅ and reverse transcriptase. Aliquot of resulting mixture is then used for polymerase chain reaction in a reaction mixture containing a primer mix corresponding to the least degenerate two of the aforementioned seven peptide fragments and Taq polymerase. The polymerase chain reaction products are analyzed by agarose gel electrophoresis and the major amplification product is excised from the gel, eluted and purified and ligated into PCRII vector for sequencing and the sequence is determined. A gene fragment including the 5' end of the gene is then obtained as follows from the total purified MRNA. Aliquot of mixture resulting from reverse transcription of total purified mRNA is primed with a gene-specific primer (based on a portion of the sequence determined for the 5' end of middle fragment). The resulting cDNA is dC-tailed at the 5' end and the 5' end is amplified by polymerase chain reaction using a nested primer having sequence based on another portion of the sequence determined for the 5' end of middle fragment and an anchor primer and the major amplification product is excised and recovered as described above and cloned into pAMP1 for sequencing and the sequence of the 5' end is determined. Next a gene fragment including the 3' end of the gene is obtained as follows from the total purified mRNA. Aliquot of resulting mixture from reverse transcription of total purified mRNA is amplified using polymerase chain reaction using a gene specific primer (based on a portion of the sequence determined for the 3' end of middle fragment) and a second round of polymerase chain reaction using a nested primer is used to provide enrichment of 3' end cDNA fragment. The polymerase chain reaction product representing the 3' end of the cDNA is cloned into pAMP1 vector for sequencing and is sequenced. Having cloned and sequenced the 5' and 3' ends of the cDNA, primers are synthesized corresponding to these ends and also incorporating BamHI and EcoRI restriction sites and these are used to amplify the entire gene sequence following the procedures described above. The gene is then cloned into the E. coli vector pBluescript which has been prepared with BamHI and EcoRI and transformed into XL1-blue cells for sequencing and sequencing provides the sequence of the entire gene. A detailed description of the isolation and identification of gene coding for acyltransferase from L. pennelli (LA716) is set forth in Example II hereinafter. Sequencing of the gene provided the sequence set forth in the Sequence Listing as SEQ ID NO: 9. The amino acid sequence corresponding to base pairs 1-54 of the nucleic acid sequence of SEQ ID NO: 9 constitutes a signal peptide. Thus, the peptide of SEQ ID NO: 1 is the fragment at the N-terminus of the enzyme. The nucleic acid sequence of SEQ ID NO: 9 indicates a discrepancy in portion corresponding to the peptide fragment of SEQ ID NO: 4 in that it indicates that the amino acid for position number 3 of the sequence of SEQ ID NO: 4 is Phe instead of Ile. Furthermore, the nucleic acid sequence of SEQ ID NO: 9 indicates a discrepancy in portion corresponding to the peptide fragment of SEQ ID NO: 7 in that it indicates that the amino acid for the position number 14 in SEQ ID NO: 7 is Cys instead of Leu. The nucleic acid sequence of SEQ ID NO: 9 after the signal peptide corresponding to base pairs 1-54 is accounted for, indicates that the acyltransferase coded for by the remainder of the base pairs should contain 446 amino acids and have a molecular mass of about 49 kDa and have the sequence set forth in the Sequence Listing as SEQ ID NO.: 10. This indicates that the acyltransferase herein is encoded by a small gene family and that the gene that was isolated was slightly different from the gene encoding the acyltransferase that was isolated.

The difference between the molecular mass determined by sodium dodecylsulfate polyacrylamide gel electrophoresis (subunit molecular masses of 33 kDa and 22 kDa for a total of 55 kDa) and that predicted for the mature protein from the sequence of the isolated gene (49 kDa) is not an unusual observation and is not of concern. The protein is glycosylated and this may result in electrophoretic behavior inconsistent with the mass of the polypeptide. Also a skewed amino acid composition of a small fragment (≦20 kDa) may result in anomalous migration on sodium dodecyl sulfate polyacrylamide gel electrophoresis.

The isolated gene is transferred into yeast by inserting the entire acyltransferase cDNA sequence into the Saccharomyces cerevisiae expression vector pYES2, to generate a plasmid pYAGT2 and transforming pYAGT2 into S. cerevisiae; expression is achieved by induction with galactose. A suitable procedure is described in more detail in Example III.

The isolated gene is transferred into E. coli (e.g., E. coli XL-Blue supplied by Stratagene) by cloning into pBluescript and transforming the resulting plasmid into E. coli via electroporation; expression is achieved by induction of the lac promoter using X-Gal (supplied by Stratagene) according to supplier's instructions.

The isolated gene is used to transform a plant, e.g., a tobacco plant, by the procedures described in Fraley, R. F., et al., CRC Critical Reviews in Plant Sciences 4: 1-86 (1986).

The embodiments of the invention are illustrated in the following working examples:

EXAMPLE I Isolation and characterization of acyltransferase from L. pennelli (LA716)

L. pennelli (LA716) seeds were obtained from Tomato Genetics Resource Center, Department of Vegetable Crops, University of California, Davis, Calif. 95616-8746, and were grown in the greenhouse. The "LA" designation is the Lycopersicon accession number. The original seed was collected on Feb. 16, 1958 by Donovan Correll at the Pacific face of the southern Peruvian Andes (latitude, 16 degrees S, by longitude 73-74 degrees W) and was deposited and accessioned in 1959. The plant of LA716 is described at pages 39-41 of Correll, Donovan Stewart, "The Potato and Its Wild Relative", Texas Research Foundation, Renner, Tex., 1962.

The following procedure was used to obtain leaf extracts: 200 g of frozen leaves and stem tissue was homogenized in 500 ml of 50 mm Hepes.NaOH, pH 7.0/250 mM sucrose (functions to stabilize protein)/10 mM dithiothreitol(inhibits oxidative browning of extract)/1% (w/v) acid-washed polyvinyl pyrrolidone (binds phenolics)/0.1% (w/v) diethyldithiocarbamate (inhibits polyphenol oxidases). The homogenate was centrifuged at 15,000×g for 20 minutes to remove debris. The supernatant was adjusted to 80% saturation with solid (NH₄)₂ SO₄ and, after 30 minutes on ice, was centrifuged at 20,000×g for 30 min. The pellet was suspended in 10 ml of 50 mM Hepes.NaOH, pH 7.0/1 mM dithiothreitol/0.5 mM phenylmethylsulfonylfluoride (inhibits protease activity)/10% (vol/vol) glycerol (functions to stabilize protein) and dialyzed against the same buffer. The specific activity of acyltransferase at this stage was 7.2×10⁻³ nkatal/mg.

The dialyzed extract was then precipitated using 0.15 to 0.22 g/ml solid polyethylene glycol (mol. wt. 3,350). The pellet resulting after centrifugation at 20,000×g for 30 min. was resuspended in 50 mM Hepes-NaOH, pH 7.0, 1 mM dithiothreitol, 0.5 mM phenylmethylsulfonylfluoride, 10% (v/v) glycerol. This resulted in a 5-fold purification of the acyltransferase activity, i.e., to a specific activity of 3.7×10⁻² nkatal/mg. This preparation was loaded on a DEAE-Sepharose column equilibrated in the same buffer, washed with ten column volumes of buffer, and eluted with a 0 to 250 mM KCl gradient. Acyltransferase activity of each fraction was monitored by enzymatic activity, and the most active fractions, which eluted around 150 mM KCl, were pooled and concentrated by ultrafiltration, yielding a 23-fold purification, i.e., to a specific activity of 0.17 nkatal/mg. The sample was then loaded on a ConA column, and washed with ten volumes of loading buffer. The column was then washed with a 50 mL portion of loading buffer brought to 50 mM α-methyl glucoside. The acyltransferase activity was then eluted with 100 mM α-methyl glucoside. The sample was then dialyzed against 50 mM Hepes-NaOH, pH 7.0 and 10% (v/v) glycerol and concentrated by ultrafiltration, resulting in a 1,274-fold purification of acyltransferase activity, i.e., to a specific activity of 9.4 nkatal/mg. This preparation was then loaded on a Mono P high pressure liquid chromatography chromatofocusing column, from which it eluted at a pH of 4.8, resulting in a 5000-fold overall purification, i.e., to a specific activity of 36 nkatal/mg.

The acyltransferase enzyme product was determined to consist of two subunits of molecular mass 33 kDa and 22 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis after the enzyme was prepared under reducing conditions on comparison to migration of proteins of known molecular weight. The standard proteins used to obtain this data were obtained from Sigma Chemical Co. and have molecular weights ranging from 66 to 14.3. These standard proteins and their molecular weights are bovine serum albumin (66 kDa), ovalbumin (45 kDa), glyceraldehyde-3-phosphate dehydrogenase (36 kDa), carbonic anhydrase (29 kDa), trypsinogen (24 kDa), trypsin inhibitor (20 kDa), and α-lactalbumin (14.3 kDa).

Molecular weight of the native enzyme was determined using Sephadex G100 column eluted with 50 mM Hepes-NaOH, pH 7.0 and 10% (v/v) glycerol. Molecular weight markers consisted of aprotinin (6.5 kDa), cytochrome c (12.4 kDa), carbonic anhydrase (29.0 kDa), serum albumin (66.0 kDa), and alcohol dehydrogenase (150 kDa). Under these conditions the acyltransferase exhibited a relative molecular mass of 100 kDa.

The isoelectric point of the enzyme was determined by electrofocusing on a 5% polyacrylamide native gel with a 3.5 to 9 pH gradient. When electrofocusing was complete, the gel was sliced horizontally into 2 mM bands each of which was suspended in H₂ O. The pH of these suspensions was measured directly and an aliquot of each tested for acyltransferase activity. The enzyme was shown to possess a pI of 5.2 under these conditions.

The 5000-fold purified acyltransferase was loaded on SDS-PAGE and electroblotted onto a poly (vinylidene difluoride) membrane following the art described by Matsudaira (Methods in Enzymology 182: 602-613 (1990). The membrane was stained with Ponceau stain and the band containing the enzyme excised and destained in methanol, and resuspended in H₂ O. The destained membrane was treated with trypsin and the resulting proteolytic products separated by high pressure liquid chromatography using a gradient from 0.1% aqueous trifluoroacetic acid to 100% acetonitrile, 0.1% trifluoroacetic acid. Seven of the resulting polypeptides were sufficiently homogeneous to sequence using automated Edman degradation procedures, and were determined respectively to have the sequences of SEQ ID NOS: 1-7.

The assays for enzyme activity in the purification steps were carried out by measuring the disproportionation of 1-O-β- ¹⁴ C-isobutyryl!glucose to di-, tri-, and tetra-isobutyryl glucose, i.e., the transfer of the ¹⁴ C!isobutyryl group from 1-O-β- ¹⁴ C-isobutyryl!glucose to other 1-O-β- ¹⁴ C-isobutyryl!glucose, in the presence of sample for which enzyme activity was being determined.

Disproportionation activity was measured by intermolecular transfer of the ¹⁴ C-isobutyryl! moiety from donor 1-O-β- ¹⁴ C-isobutyryl!-β-D-glucoses to recipient 1-O-β- ¹⁴ C-isobutyryl!-β-D-glucoses, resulting in formation of higher-order glucose esters of isobutyrate. Reactions were performed in a total volume of 15 μL which contained 50 mM Hepes, pH 7.5, 10 mM dithiothreitol, 1 mM 1-O- ¹⁴ C-isobutyryl!-β-D-glucose (10⁵ cpm), and 1 to 100 ng acyltransferase. The reaction was allowed to proceed at 37° C. for 30 min., and then loaded onto a silica gel thin-layer chromatography plate and eluted in chloroform/methanol/water (75:22:3). The thin-layer plate was then dried, exposed to autoradiographic film, and upon development of the autoradiographic image, the silica gel at regions corresponding to the point of migration of di-, tri-, and tetra- ¹⁴ C-isobutyryl!-glucose was scraped from the plate, eluted with methanol, and radioactivity quantified by liquid scintillation.

The purified enzyme was tested for activity against the carboxypeptidase substrates carbobenzoxy-phe-ala, carbobenzoxy phe-leu, carbobenzoxy-gly-phe and carbobenzoxy-pro-phe. No activity was detected against any of these substrates.

EXAMPLE II Isolation of Gene Coding for Acyltransferase from L. pennelli (LA716)

Detached trichomes were obtained from leaves of L. pennelli (LA716) by dry ice abrasion as described in Yerger, E. H., et al., Plant Physiol 99, 1-7 (1992) except that pulverized dry ice was first sieved through a fiberglass screen (1.4 mm² mesh). The trichomes were suspended in freshly prepared Tris.HCl, pH 7.0 (buffer)/1 mM MgCl₂ (stabilizer of protein structure and enzymatic activity)/0.1% diethyldithiocarbamate (acts as copper chelator to inhibit polyphenol oxidase)/0.1% dithiothreitol (acts as copper chelator to inhibit polyphenol oxidase and as scavenger of quinones, the reaction product of polyphenol oxidase)/2% polyvinylpolypyrrolidone (inhibitor of polyphenol oxidase; acts as scavenger of phenolics, the substrates for polyphenol oxidase).

Total RNA was extracted from the trichomic suspension and mRNA was purified according to the method described in Hunt, M. D., et al., Plant Molec. Biol. 21, 59-68 (1993).

A acyltransferase gene was cloned following procedures described by Frohman, M. A., et al., Proc. Natl. Acad. Sci. USA 85:8998-9002 (1988), and Loh, E. Y., et al., Science 243:217-220 (1980).

Sequence of an internal fragment of the gene coding for acyltransferase was determined as follows:

The purified mRNA was reversed transcribed into cDNA using olig (dT)₁₅ and reverse transcriptase (Superscript II RNase H-, Gibco-BRL, used with 0.1 μg mRNA in 10 μL reaction according to manufacturer's instructions).

One μL resulting mixture was then used for polymerase chain reaction in a 100 μL reaction mixture containing 10 mM Tris-HCl 8.3, 50 mM KCl, 1.5 mM MgCl₂, 0.1% (w/v) gelatin, 200 μM dNTPs, 3.2 μM of 20 base primer PT 50 (having the sequence set forth in the Sequence Listing as SEQ ID NO: 11), 1.6 μM primer RE24 (having the Sequence Listing as SEQ ID NO: 12, and 2.5 Units Taq polymerase. In the sequence of SEQ ID NO: 12, N stands for inosine. The primers PT50 and RE24 correspond to the least degenerate two of the seven polypeptides referred to and described in terms of sequences in Example I. Polymerase chain reaction was carried out in 34 cycles of denaturing (92° C., 1 min.), annealing (50° C., 40 sec.), and polymerization (72° C., 1 min.) and one cycle of 72° C., 10 min. The polymerase chain reaction products were analyzed by agarose gel electrophoresis and the major amplification product was excised from the gel, eluted and purified using GeneCleanII nucleic acid clean up kit (available from Bio 101), following the manufacturer's instructions, and ligated into PCRII vector (supplied by Invitrogen) following the ATR cloning method (provided by Invitrogen). DNA sequencing was carried out to verify the amplified fragment as a component of the acyltransferase gene and to identify the sequences corresponding to the tryptic peptides (corresponding to the primers used) obtained from the purified enzyme and to provide sequencing information for primers to obtain the 5' and 3' ends of the acyltransferase gene as described below.

Gene fragment including the 5' end of the gene was then obtained as follows: Aliquot of mixture resulting from the reverse transcription of total purified mRNA was primed with a 20 base pair gene-specific primer having the sequence set forth in the Sequence Listing SEQ ID NO: 13 (based on a portion of the sequence determined as described above for 5' end of middle fragment). The resulting cDNA was dc-tailed at the 5' end and the 5' end was amplified by polymerase chain reaction using a 20 base pair nested primer having the sequence set forth in the Sequence Listing as SEQ ID NO: 14 (based on another portion of the sequence determined as described above for the 5' end of the middle fragment) and an anchor primer having the sequence set forth in the Sequence Listing as SEQ ID NO: 15 (Gibco-BRL catalog #18388-017). In the sequence of SEQ ID NO: 15, N is inosine. The major amplification product is excised and recovered as described above and cloned into pAMP1 (Gibco-BRL), following the manufacturer's instructions, and sequenced.

Next gene fragment including the 3' end of the gene was obtained as follows: cDNA was synthesized from purified mRNA using reverse transcription primed with Oligo (dT) primer attached to an adapter primer. The 3' end of the cDNA was amplified using Gibco-BRL 3' RACE (rapid amplification of cDNA ends) kit. In a first round of amplification, a 20 base pair primer (based on a portion of the sequence determined as described above for the 3' end of the middle fragment) having the sequence set forth in the Sequence Listing as SEQ ID NO: 16, was used. A second round of polymerase chain reaction was then carried out using a 20 base pair nested primer (based on another portion of the sequence determinated as described above for the 3' end of the middle fragment) having the sequence set forth in the Sequence Listing as SEQ ID NO: 17, to enrich the 3' end cDNA fragment. The polymerase chain reaction product was cloned into pAMP1 (Gibco-BRL) following the manufacturer's instructions, and sequenced.

Having cloned and sequenced the 5' and 3' ends of the cDNA, primers were synthesized corresponding to these ends and also incorporating BamHI and EcoRI restriction sites and these were used to amplify the entire acyltransferase gene sequence from the CDNA obtained from purified MRNA. The primers used respectively had the sequence set forth in the Sequence Listing as SEQ ID NO: 18 (includes a BamHI restriction site as the first nine bases of the sequence) and the sequence set forth in the Sequence Listing as SEQ ID NO: 19 (includes an EcoRI restriction site as the first seven bases of the sequence). The amplified entire gene was cloned into the E. coli vector pBluescript (supplied by Stratagene) which was prepared with BamHI and EcoRI and transformed into XL1-Blue E. coli cells (from Stratagene) according to the supplier's instructions, for sequencing.

The gene was sequenced by automatic DNA sequencing and was determined to have the sequence set forth in the Sequence Listing as SEQ ID NO: 9.

EXAMPLE III Transformation of Gene Coding for Acyltransferase into S. cerevisiae and Induction of Expression of Acyltransferase

A. Construction of expression clone pYAGT2 By Inserting Entire Acyltransferase cDNA Sequence into the Saccharomyces cerevisiae Expression Vector pYES2. to Generate Plasmid pYAGT2

Oligonucleotide primers corresponding to the acyltransferase 5' and 3' ends and incorporating BamHI and EcoRI restriction sites were used to amplify the gene (isolated in Example II) directly from the cDNA by polymerase chain reaction. The primers respectively have the sequences set forth in the Sequence Listing as SEQ ID NO: 18 and as SEQ ID NO: 19. After purification and treatment with BamHI and EcoRI, the gene was ligated, using T4 DNA ligase, to the Saccharomyces cerevisiae expression vector pYES2 (Invitrogen), which was prepared by the same restriction enzymes. The resulting plasmid was designated pYAGT2. To verify that correct gene was ligated, the ligation reaction was transformed into XL-1Blue E. coli cells, and the correctly ligated products from transformants were verified by DNA sequencing. The plasmid pYAGT2 was deposited with the American Type Culture Collection, 12301 Parklawn Drive, Rockville, Md. 20852 on Jun. 15, 1996 under the terms of the Budapest Treaty and has been assigned accession number ATCC 97613.

B. Transforming pYAGT2 into S. cerevisiae

S. cerevisiae strain KT1115 (MATa leu2-3 leu2-112 ura-52) is used as the recipient cell type for pYES2 transformation following the procedures described by Gietz, D., et al., Nucleic Acids Research 20:1425 (1992). Uracil dropout medium (Short Protocols in Molecular Biology, A Compendium of Methods from Current Protocols in Molecular Biology, Ausubel, F. M., et al., editors, 2nd Edition, Green Publishing Associates and John Wiley and Sons, New York, 1992) was used as selective medium.

C. Induction of Expression of Protein Encoded by the Recombinant Plasmid

Baffled flasks were used to grow yeast cultures for the expression of the L. pennelli acyltransferase. Transformed yeast cells were inoculated in uracil dropout medium (with 5% (w/v) raffinose instead of 2% (w/v) glucose), until OD₆₀₀ reached 0.4 to 0.5. Galactose was then added to a final concentration of 2% (w/v) to induce expression of the protein. 10 mL samples were collected at 4, 8, 24 and 48 hours after the addition of galactose.

D. Determination of Expressed Protein as Being Acyltransferase

Induced cells were centrifuged, washed with cold H₂ O and then with cold FT buffer, i.e., freeze and thaw buffer: 100 mM Hepes, pH 7.5, 20% (v/v) glycerol, 0.1% (v/v) Triton X-100). The pelleted cells were resuspended in an equal volume of cold FT buffer and frozen at -80° C. overnight or longer. For assay for activity, the permeabilized cells were thawed quickly at 30° C. and an aliquot removed as described by Miozzari (Miozzari, G. F., et al., Analytical Biochemistry 90:220-233 (1978)). When 10 mL of cells were removed for assay under standard conditions for measurement of acyltransferase activity using 1-O- ¹⁴ C-isobutyryl!-β-glucose as described above, S. cerevisiae cells transformed with only the pYES2 vector do not possess detectable acyltransferase activity giving rise to higher-order glucose esters at any time-point after induction with galactose. However, S. cerevisiae cells harboring the pYAGT2 plasmid containing the acyltransferase gene exhibited the ability to form higher-order esters at 4, 8 and 24 hours after induction with galactose showing acyltransferase activity was expressed. Highest activity was found 24 hours after induction, and activity at 48 hours was slightly lower than at 24 hours.

EXAMPLE IV Preparation of Monopalmitoyl Glucose from 1-O-Palmitoyl-β-D-glucose and Glucose

Tetrabenzylglucose (1.8 g, 3.3 mmol), Pfanstiehl Chemical Co., was reacted with palmitoyl chloride (Sigma Chemical Co.) in dry benzene at 62° C. and deprotected by the procedure of Pfeffer, P. E., et al., J. Org. Chem. 41, 2925-2927 (1976), to produce 1-O-palmitoyl-β-D-glucose.

A reaction mix was made up containing 2 mM 1-O-palmitoyl-β-D-glucose, 40 μM U-¹⁴ C! glucose (2×10⁵ cpm) and 1 mg/ml of acyltransferase protein (specific activity of 4×10⁻² nanokatals mg⁻¹) in 15 μl of a mixture of 50 mm Hepes-NaOH, pH 7.0 (buffer), 10 mM MgCl₂ (stabilizer of protein structure and enzymymatic activity), and 10 mM dithiothreitol (inhibitor of polyphenol oxidase; acts as copper chelator and as scavenger of quinones, the reaction product of polyphenol oxidase; also promotes higher order esterification presumably by maintaining essential Cys residues of the acyltransferase in reduced form) and incubation was carried out at 37° C. Reaction progress was monitored by TLC as described in Ghangas, G. S. et al., Proc. Natl. Acad. Sci. USA 90, 9911-9915 (1993). The % cpm in monoacyl- ¹⁴ C! glucose was 2.3 after 1 hour, 4.4 after 2 hours and 4.7 after 3 hours.

When 1-O-isobutyryl-β-D-glucose was substituted for the 1-O-palmitoyl-β-D-glucose, the % cpm in monoacyl- ¹⁴ C! glucose was 3.08 after 1 hour, 5.80 after 2 hours, and 6.20 after 3 hours.

EXAMPLE V Preparation of Dipalmitoyl Glucose from 1-O-palmitoyl-β-D-glucose

1-O-Palmitoyl-β-D-glucose (0.1mM) and 80 μM U-¹⁴ C! glucose (2×10⁷ cpm) were incubated with 1 mg acyltransferase (specific activity of about 0.037 nanokatals mg⁻¹) from L. pennelli in 0.5 ml 50 mM sodium Pi, pH 6.5, for 2 hours at 42° C. The reaction was stopped by addition of 1 ml of chilled ethanol, and after centrifugation, the supernatant was recovered, concentrated, and applied to a preparative TLC plate to isolate the 1-O-palmitoyl-β-D- ¹⁴ C-glucose! band.

Reaction mix was made up containing 3×10⁴ cpm 1-O-palmitoyl-β-D- ¹⁴ C-glucose!, 50 mM Hepes-NaOH, pH 7.0, 10 mM dithiothreitol (inhibits oxidation browning), 10 mM MgCl₂ (protein structure stabilizer) and acyltransferase (3.6 mg/mL protein; specific activity of about 0.037 nanokatal mg⁻¹) from L. pennelli in 15 μl were incubated at 37° C. The products were separated and monitored by TLC as described in Ghangas, G. S., et al., Proc. Natl. Acad. Sci. USA 90, 9911-9915 (1993). The percent of total cpm in ¹⁴ C! glucose by-product was 40% indicating that the disproportion reaction had occurred to provide dipalmitoyl glucose.

When 1-O-isobutyryl-β-D-glucose was substituted for the 1-O-palmitoyl-β-D-glucose, the percent of total cpm in ¹⁴ C! glucose by-product was 44.8% indicating that the disproportion reaction had occurred to provide diisobutyryl glucose.

EXAMPLE VI Preparation of Tripalmitoyl Glucose from 1-O-Palmitoyl-β-D-glucose

A 15 μL reaction containing 1-O-palmitoyl-β-D-glucose (1 mM), U-¹⁴ C!-glucose (2×10⁵ cpm), and 2.5 mg L. pennellii LA716 crude leaf extract protein/ml in 100 mM sodium phosphate pH 6.5 was incubated for 28 hr at 37° C. The products were separated and monitored by TLC as described in Ghangas GS and Steffens JC, Proc. Natl. Acad. Sci. USA 90:9911-9915 (11/93). The percent of total cpm converted to tripalmitoylglucose was equivalent to 8 pmol. Formation of mono- and dipalmitoylglucose in the same reaction was 2660 and 459 pmol, respectively. Under the same conditions 1-O-isobutyryl-β-D-glucose yielded 3410, 34 and 14 pmol mono-, di- and triisobutryrylglucose, respectively.

Variations in the invention will be obvious to those skilled in the art. Therefore, the invention is defined by the claims.

    __________________________________________________________________________     SEQUENCE LISTING                                                               (1) GENERAL INFORMATION:                                                       (iii) NUMBER OF SEQUENCES: 19                                                  (2) INFORMATION FOR SEQ ID NO:1:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 12 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: peptide                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:                                        GluHisPheIleValGluThrLeuProGlyPheHis                                           1510                                                                           (2) INFORMATION FOR SEQ ID NO:2:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 8 amino acids                                                      (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: peptide                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:                                        LeuGluLeuAsnSerTyrSerTrp                                                       15                                                                             (2) INFORMATION FOR SEQ ID NO:3:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 11 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: peptide                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:                                        IleTyrAspGlyIleGluValGlyAspArgPro                                              1510                                                                           (2) INFORMATION FOR SEQ ID NO:4:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 11 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: peptide                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4:                                        GlyTyrIleGlnGlyAsnAlaLeuThrAspArg                                              1510                                                                           (2) INFORMATION FOR SEQ ID NO:5:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 7 amino acids                                                      (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: peptide                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:5:                                        SerIleAspPheAsnGlyArg                                                          15                                                                             (2) INFORMATION FOR SEQ ID NO:6:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 11 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: peptide                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6:                                        TyrAlaAsnHisMetGlyLeuIleSerAspLys                                              1510                                                                           (2) INFORMATION FOR SEQ ID NO:7:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 17 amino acids                                                     (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: peptide                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7:                                        AsnGlyAsnTyrIleAspValAspProAsnAsnIleLeuLeuLeuAsn                               151015                                                                         Asp                                                                            (2) INFORMATION FOR SEQ ID NO:8:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 179 amino acids                                                    (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: peptide                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:8:                                        GluHisPheIleValGluThrLeuProGlyPheHisGlyLysLeuPro                               151015                                                                         PheLeuThrGluThrGlyThrIleSerValGlyGluGluGluLysVal                               202530                                                                         GlnLeuPheTyrPhePheValGlnSerGluArgAspProArgAsnAsp                               354045                                                                         ProLeuMetIleTrpLeuThrGlyGlyProGlyCysSerGlyLeuSer                               505560                                                                         SerLeuValTyrGluIleGlyProLeuThrPheAspTyrAlaAsnSer                               65707580                                                                       SerGlyAsnPheProLysLeuGluLeuAsnSerTyrSerTyrThrLys                               859095                                                                         ValAlaAsnIleIlePheIleAspGlnProAlaGlyThrGlyTyrSer                               100105110                                                                      TyrAlaAsnThrSerGluAlaTyrAsnCysAsnAspThrLeuSerVal                               115120125                                                                      ThrLeuThrTyrAspPheLeuArgLysTrpLeuMetAspHisProGlu                               130135140                                                                      TyrLeuAsnAsnProLeuTyrValGlyGlyAspSerTyrSerGlyIle                               145150155160                                                                   PheValAlaLeuLeuThrArgLysIleTyrAspGlyIleGluValGly                               165170175                                                                      AspArgPro                                                                      (2) INFORMATION FOR SEQ ID NO:9:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 1604 base pairs                                                    (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: double                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (ix) FEATURE:                                                                  (A) NAME/KEY: CDS                                                              (B) LOCATION: 55..1392                                                         (xi) SEQUENCE DESCRIPTION: SEQ ID NO:9:                                        ATGGCGCGGGTCACACTGTTTCTATTGCTGCTACTTGTATACGGTGTAGTCTCCGAG57                    Glu                                                                            CACTTCATTGTTGAAACTCTTCCTGGGTTTCATGGAAAACTTCCATTT105                            HisPheIleValGluThrLeuProGlyPheHisGlyLysLeuProPhe                               51015                                                                          ACACTCGAAACTGGTTATATTAGTGTTGGAGAAGAGGAAAAAGTGCAG153                            ThrLeuGluThrGlyTyrIleSerValGlyGluGluGluLysValGln                               202530                                                                         CTATTTTATTTCTTTGTACAATCTGAGAGAGACCCACGAAATGATCCT201                            LeuPheTyrPhePheValGlnSerGluArgAspProArgAsnAspPro                               354045                                                                         CTCATGATTTGGCTCACCGGAGGTCCTGGTTGTTCTGGTCTGTCTTCC249                            LeuMetIleTrpLeuThrGlyGlyProGlyCysSerGlyLeuSerSer                               50556065                                                                       TTAGTATATGAAATTGGCCCTTTAACCTTTGATTATGCAAATTCTAGT297                            LeuValTyrGluIleGlyProLeuThrPheAspTyrAlaAsnSerSer                               707580                                                                         GGAAATTTCCCGAAACTGGAGTTGAACTCATATTCTTGGACCAAGGTG345                            GlyAsnPheProLysLeuGluLeuAsnSerTyrSerTrpThrLysVal                               859095                                                                         GCAAACATAATATTTATAGATCAACCTGCTGGCACAGGCTACTCATAT393                            AlaAsnIleIlePheIleAspGlnProAlaGlyThrGlyTyrSerTyr                               100105110                                                                      GCAAACACTTCAGAAGCTTACAACTGCAATGATACCCTCTCTGTAACT441                            AlaAsnThrSerGluAlaTyrAsnCysAsnAspThrLeuSerValThr                               115120125                                                                      CTAACTTATGACTTCCTTAGAAAGTGGCTTATGGATCATCCCGAGTAT489                            LeuThrTyrAspPheLeuArgLysTrpLeuMetAspHisProGluTyr                               130135140145                                                                   CTCAACAATCCACTATATGTTGGTGGTGATTCCTACTCAGGCATTTTT537                            LeuAsnAsnProLeuTyrValGlyGlyAspSerTyrSerGlyIlePhe                               150155160                                                                      GTTGCACTGCTTACTCGCAAAATATACGATGGTATTGAAGTTGGTGAC585                            ValAlaLeuLeuThrArgLysIleTyrAspGlyIleGluValGlyAsp                               165170175                                                                      AGGCCTCGAGTTATTATCAAAGGATATTTCCAAGGAAATGCTCTAACA633                            ArgProArgValIleIleLysGlyTyrPheGlnGlyAsnAlaLeuThr                               180185190                                                                      GATAGATCCATCGACTTCAATGGTAGAGTCAAATATGCTAATCATATG681                            AspArgSerIleAspPheAsnGlyArgValLysTyrAlaAsnHisMet                               195200205                                                                      GGACTTATTTCAGATAAGATCTATCAGTCTGCTAAAGCAAATTGCAAC729                            GlyLeuIleSerAspLysIleTyrGlnSerAlaLysAlaAsnCysAsn                               210215220225                                                                   GGGAATTACATTGACGTTGATCCAAATAACATATTATGCCTAAATGAT777                            GlyAsnTyrIleAspValAspProAsnAsnIleLeuCysLeuAsnAsp                               230235240                                                                      CTTCAGAAAGTAACAAGGTGTCTCAAGAACATACGACGGGCGCAAATT825                            LeuGlnLysValThrArgCysLeuLysAsnIleArgArgAlaGlnIle                               245250255                                                                      TTAGAGCCTTACTGTGACCTTCCATATTTAATGGGTATTCTCCAAGAA873                            LeuGluProTyrCysAspLeuProTyrLeuMetGlyIleLeuGlnGlu                               260265270                                                                      ACTCCTACAAATGGCCAGTCAGTATTTCCAATTGCAGGACCATGGTGT921                            ThrProThrAsnGlyGlnSerValPheProIleAlaGlyProTrpCys                               275280285                                                                      CGAGAAAAGAATTACATATACTCGTATGTTTGGGCAAATGATAAAGCT969                            ArgGluLysAsnTyrIleTyrSerTyrValTrpAlaAsnAspLysAla                               290295300305                                                                   GTCCAGAAAGCACTAAGCGTTCGTGAGGGAACAACATTGGAGTGGGTG1017                           ValGlnLysAlaLeuSerValArgGluGlyThrThrLeuGluTrpVal                               310315320                                                                      AGATGCAATGAAAGCATGCATTATAGAGGTAAGGAGAGAACCGAGTCA1065                           ArgCysAsnGluSerMetHisTyrArgGlyLysGluArgThrGluSer                               325330335                                                                      TATGTGTATGATGTCCCAAGTGTCATTGATGATCATCAACATCTCACC1113                           TyrValTyrAspValProSerValIleAspAspHisGlnHisLeuThr                               340345350                                                                      AGCAAATCCTGTCGAGCACTAATTTACAGTGGTGACCATGACATGGTT1161                           SerLysSerCysArgAlaLeuIleTyrSerGlyAspHisAspMetVal                               355360365                                                                      GTTCCTCATTTGAGCACGGAGGAATGGATAGAGACTTTGAAACTTCCA1209                           ValProHisLeuSerThrGluGluTrpIleGluThrLeuLysLeuPro                               370375380385                                                                   ATTGCAGATGATTGGGAGCCTTGGTTTGTTGACGATCAAGTAGCAGGA1257                           IleAlaAspAspTrpGluProTrpPheValAspAspGlnValAlaGly                               390395400                                                                      TACAAAGTGAAGTATTTACAAAATGATTATGAAATGACATATGCAACT1305                           TyrLysValLysTyrLeuGlnAsnAspTyrGluMetThrTyrAlaThr                               405410415                                                                      GTTAAGGGTGCGGGGCATACTGCTCCTGAATACAAGCCAGAACAATGC1353                           ValLysGlyAlaGlyHisThrAlaProGluTyrLysProGluGlnCys                               420425430                                                                      CTGCCCATGGTTGATAGGTGGTTTTCCGGTGACCCTCTTTGATTTCACC1402                          LeuProMetValAspArgTrpPheSerGlyAspProLeu                                        435440445                                                                      CTTGCAAGACATTAATGTACTCATTTGTTTCTCTGGATTGACATAAGCTTGCTTCTTTGA1462               GCAACATCACATTAAGCTTGTCTGTCATGTAATCTTGACATGTAAAATCACACATTAAAA1522               AGTATATATCATTCGAGGTTGACGTTAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA1582               AAAAAAAAAAAAAAAAAAAAAA1604                                                     (2) INFORMATION FOR SEQ ID NO:10:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 446 amino acids                                                    (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:10:                                       GluHisPheIleValGluThrLeuProGlyPheHisGlyLysLeuPro                               151015                                                                         PheThrLeuGluThrGlyTyrIleSerValGlyGluGluGluLysVal                               202530                                                                         GlnLeuPheTyrPhePheValGlnSerGluArgAspProArgAsnAsp                               354045                                                                         ProLeuMetIleTrpLeuThrGlyGlyProGlyCysSerGlyLeuSer                               505560                                                                         SerLeuValTyrGluIleGlyProLeuThrPheAspTyrAlaAsnSer                               65707580                                                                       SerGlyAsnPheProLysLeuGluLeuAsnSerTyrSerTrpThrLys                               859095                                                                         ValAlaAsnIleIlePheIleAspGlnProAlaGlyThrGlyTyrSer                               100105110                                                                      TyrAlaAsnThrSerGluAlaTyrAsnCysAsnAspThrLeuSerVal                               115120125                                                                      ThrLeuThrTyrAspPheLeuArgLysTrpLeuMetAspHisProGlu                               130135140                                                                      TyrLeuAsnAsnProLeuTyrValGlyGlyAspSerTyrSerGlyIle                               145150155160                                                                   PheValAlaLeuLeuThrArgLysIleTyrAspGlyIleGluValGly                               165170175                                                                      AspArgProArgValIleIleLysGlyTyrPheGlnGlyAsnAlaLeu                               180185190                                                                      ThrAspArgSerIleAspPheAsnGlyArgValLysTyrAlaAsnHis                               195200205                                                                      MetGlyLeuIleSerAspLysIleTyrGlnSerAlaLysAlaAsnCys                               210215220                                                                      AsnGlyAsnTyrIleAspValAspProAsnAsnIleLeuCysLeuAsn                               225230235240                                                                   AspLeuGlnLysValThrArgCysLeuLysAsnIleArgArgAlaGln                               245250255                                                                      IleLeuGluProTyrCysAspLeuProTyrLeuMetGlyIleLeuGln                               260265270                                                                      GluThrProThrAsnGlyGlnSerValPheProIleAlaGlyProTrp                               275280285                                                                      CysArgGluLysAsnTyrIleTyrSerTyrValTrpAlaAsnAspLys                               290295300                                                                      AlaValGlnLysAlaLeuSerValArgGluGlyThrThrLeuGluTrp                               305310315320                                                                   ValArgCysAsnGluSerMetHisTyrArgGlyLysGluArgThrGlu                               325330335                                                                      SerTyrValTyrAspValProSerValIleAspAspHisGlnHisLeu                               340345350                                                                      ThrSerLysSerCysArgAlaLeuIleTyrSerGlyAspHisAspMet                               355360365                                                                      ValValProHisLeuSerThrGluGluTrpIleGluThrLeuLysLeu                               370375380                                                                      ProIleAlaAspAspTrpGluProTrpPheValAspAspGlnValAla                               385390395400                                                                   GlyTyrLysValLysTyrLeuGlnAsnAspTyrGluMetThrTyrAla                               405410415                                                                      ThrValLysGlyAlaGlyHisThrAlaProGluTyrLysProGluGln                               420425430                                                                      CysLeuProMetValAspArgTrpPheSerGlyAspProLeu                                     435440445                                                                      (2) INFORMATION FOR SEQ ID NO:11:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 20 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (xi) SEQUENCE DESCRIPTION: SEQ ID NO:11:                                       GARCAYTTYATYGTKGARAC20                                                         (2) INFORMATION FOR SEQ ID NO:12:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 20 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (ix) FEATURE:                                                                  (A) NAME/KEY: misc.sub.-- feature                                              (B) LOCATION: 3                                                                (D) OTHER INFORMATION: /note= "N is inosine"                                   (xi) SEQUENCE DESCRIPTION: SEQ ID NO:12:                                       ARNCCCATRTGRTTWGCRTA20                                                         (2) INFORMATION FOR SEQ ID NO:13:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 20 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (xi) SEQUENCE DESCRIPTION: SEQ ID NO:13:                                       ATCTGTTAGAGCATTGCCTT20                                                         (2) INFORMATION FOR SEQ ID NO:14:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 20 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (xi) SEQUENCE DESCRIPTION: SEQ ID NO:14:                                       GCCTGTCACCAACTTCAATA20                                                         (2) INFORMATION FOR SEQ ID NO:15:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 48 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (ix) FEATURE:                                                                  (A) NAME/KEY: misc.sub.-- feature                                              (B) LOCATION: 36                                                               (D) OTHER INFORMATION: /note= "N is inosine"                                   (ix) FEATURE:                                                                  (A) NAME/KEY: misc.sub.-- feature                                              (B) LOCATION: 37                                                               (D) OTHER INFORMATION: /note= "N is inosine"                                   (ix) FEATURE:                                                                  (A) NAME/KEY: misc.sub.-- feature                                              (B) LOCATION: 41                                                               (D) OTHER INFORMATION: /note= "N is inosine"                                   (ix) FEATURE:                                                                  (A) NAME/KEY: misc.sub.-- feature                                              (B) LOCATION: 42                                                               (D) OTHER INFORMATION: /note= "N is inosine"                                   (ix) FEATURE:                                                                  (A) NAME/KEY: misc.sub.-- feature                                              (B) LOCATION: 46                                                               (D) OTHER INFORMATION: /note= "N is inosine"                                   (ix) FEATURE:                                                                  (A) NAME/KEY: misc.sub.-- feature                                              (B) LOCATION: 47                                                               (D) OTHER INFORMATION: /note= "N is inosine"                                   (xi) SEQUENCE DESCRIPTION: SEQ ID NO:15:                                       CUACUACUACUAGGCCACGCGTCGACTAGTACGGGNNGGGNNGGGNNG48                             (2) INFORMATION FOR SEQ ID NO:16:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 20 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (xi) SEQUENCE DESCRIPTION: SEQ ID NO:16:                                       GTTGGAGAAGAGGAAAAAGT20                                                         (2) INFORMATION FOR SEQ ID NO:17:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 20 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (xi) SEQUENCE DESCRIPTION: SEQ ID NO:17:                                       TACAATCTGAGAGAGACCCA20                                                         (2) INFORMATION FOR SEQ ID NO:18:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 29 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (xi) SEQUENCE DESCRIPTION: SEQ ID NO:18:                                       AAGGATCCAATGGCGCGGGTCACACTGTT29                                                (2) INFORMATION FOR SEQ ID NO:19:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 27 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (xi) SEQUENCE DESCRIPTION: SEQ ID NO:19:                                       AGAATTCTTAACGTCAACCTCGAATGA27                                                  __________________________________________________________________________ 

What is claimed is:
 1. An essentially pure acyltransferase which catalyzes transfer of C₁ -C₁₈ straight or branched chain, saturated or unsaturated acyl substituents to produce sugar esters and sugar polyesters with C₁ -C₁₈ straight or branched chain, saturated or unsaturated acyl substituents which comprises the sequence set forth in the Sequence Listing as SEQ ID NO:8.
 2. The essentially pure acyltransferase of claim 1 further comprises the sequences set forth in the Sequence Listing as SEQ ID NOS: 5 and
 6. 3. The essentially pure acyltransferase of claim 2 which comprises the sequence set forth in the Sequence Listing as SEQ ID NO:
 10. 4. A purified acyltransferase which catalyzes transfer of C₁ -C₁₈ straight or branched chain, saturated or unsaturated acyl substituents to produce sugar esters and sugar polyesters with C₁ -C₁₈ straight or branched chain, saturated or unsaturated acyl substituents which comprises the sequences set forth in the Sequence Listing as SEQ ID NOS:1-7.
 5. An isolated DNA molecule encoding acyltransferase which catalyzes transfer of C₁ -C₁₈ straight or branched chain, saturated or unsaturated acyl substituents to produce sugar esters and sugar polyesters with C₁ -C₁₈ straight or branched chain, saturated or unsaturated acyl substituents which comprises the sequence set forth in the Sequence Listing as SEQ ID NO:9.
 6. A method for preparing palmitoyl esters of glucose which comprises reacting 1-O-palmitoyl-β-D-glucose with glucose or palmitoyl partial ester of glucose in the presence of purified acyltransferase which catalyzes transfer of palmitoyl substituent from 1-O-palmitoyl-β-D-glucose to glucose or palmitoyl partial ester of glucose to produce said palmitoyl esters of glucose.
 7. A purified acyltransferase which catalyzes transfer of C₁ -C₁₈ straight or branched chain, saturated or unsaturated acyl substituents to produce sugar esters and sugar polyesters with C₁ -C₁₈ straight or branched chain, saturated or unsaturated acyl substituents.
 8. The purified acyltransferase of claim 7 which comprises the sequences identified in the Sequence Listing as SEQ ID NOS:1, 2, and
 3. 9. The purified acyltransferase of claim 7 which comprises the sequences identified in the Sequence Listing as SEQ ID NOS:1, 2, 3, 5, and
 6. 10. An isolated DNA molecule coding for acyltransferase which catalyzes transfer of C₁ -C₁₈ straight or branched chain, saturated or unsaturated acyl substituents to produce sugar esters and sugar polyesters with C₁ -C₁₈ straight or branched chain, saturated or unsaturated acyl substituents, which is amplified in a polymerase chain reaction using primers having sequences identified in the Sequence Listing as SEQ ID NO:18 and SEQ ID NO:19.
 11. The method of claim 6 wherein the acyltransferase comprises the sequences identified in the Sequence Listing as SEQ ID NOS:1, 2 and
 3. 12. The method of claim 6 wherein the acyltransferase comprises the sequence set forth in the Sequence Listing as SEQ ID NO:8.
 13. A purified acyltransferase which catalyzes transfer of the acyl substituent from 1-O-acyl-β-D-glucose to glucose, 2-deoxyglucose, 3-O-methyl glucose or partially acylated glucose and disproportionation between two molecules of 1-O-acyl-β-D-glucose resulting in formation of diacylglucose and glucose, where the acyl substituents contain 1 to 18 carbon atoms and are branched or straight chain and saturated or unsaturated, and which comprises the sequences set forth in the Sequence Listing as SEQ ID NOS:1-7, and which has a native molecular weight of 100,000 Da on a gel permeation column, and an isoelectric point as determined by isoelectric focusing on a 5% polyacrylamide native gel with a 3.5 to 9 pH gradient, of 5.2.
 14. A purified acyltransferase having the same sequence as that of the expression product of pYATG2 transformed into yeast. 